Elements that are required to comply serving a *primary function (accessible route to the altered area and the parking, restrooms, telephones, and drinking fountains) that comply with the 1994 TAS are not required to be brought up to the 2012 TAS unless those elements are part of the scope being altered. 

The important thing to remember here is that those elements required to comply serving a renovation to the primary function must comply with the 1994 TAS, otherwise are required to meet the minimum requirements of the 2012 TAS when renovating an area containing the major activity for which the facility is intended. 
*A "primary function" is a major activity for which the facility is intended. Areas that contain a primary function include, but are not limited to, the customer services lobby of a bank, the dining area of a cafeteria, the meeting rooms in a conference center, as well as offices and other work areas in which the activities of the public accommodation or other private entity using the facility are carried out. Mechanical rooms, boiler rooms, supply storage rooms, employee lounges or locker rooms, janitorial closets, entrances, corridors, and restrooms are not areas containing a primary function. 

 
 
Public accommodations and commercial facilities must follow the requirements of the 2010 Standards, including both the Title III regulations at 28 CFR part 36, subpart D; and the 2004 ADAAG at 36 CFR part 1191, appendices B and D. In Texas the 2012 Texas Accessibility Standards that include necessary clarifications must also be followed. 

The compliance date for the 2010 Standards for new construction and alterations is determined by:
  • the date the last application for a building permit or permit extension is certified to be complete by a State, county, or local government;
  • the date the last application for a building permit or permit extension is received by a State, county, or local government, where the government does not certify the completion of applications; or 
  • the start of physical construction or alteration, if no permit is required. 
If that date is on or after March 15, 2012, then new construction and alterations must comply with the 2010 Standards.  If that date is on or after September 15, 2010, and before March 15, 2012, then new construction and alterations must comply with either the 1991 or the 2010 Standards.

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One of the most common ramp violations is also one that can be quite tricky and costly to fix. Simple planning can prevent major issues with the ramp handrail extensions.

The 1994 Standards require that "if handrails are not continuous, they shall extend at least 12 in beyond top and bottom of the ramp segment and shall be parallel with the floor or ground surface".  What is not clearly mentioned here is that the 12" level handrail extensions must also extend in the direction of the ramp and must be AFTER the ramp segment. The 2010 Standards have clarified this: 505.10 "Handrail gripping surfaces shall extend beyond and in the same direction of stair flights and ramp runs in accordance with 505.10. Also, when planning the construction of the ramp - Always take into account where the ramp terminates near corridors and walkways. It is critical to ensure that the ramp segment begins/ends at least 12" BEFORE the perpendicular walkways and that the level 12" minimum extensions are provided at ramp landings - not sloped surface - see images

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Just when you thought your curb ramp design/construction is right - think again!  TAS 4.7.2 requires compliance with 4.8.2 which requires "the least possible slope ..used for any ramp. The maximum slope of a ramp in new construction shall be 1:12." 
That said, most curb ramps are designed to the greatest possible slope - And constructed at the standard 6' in length. 

As we all know 1:12 (8.33%) slope, 6" high, provides a 6' long curb ramp. Curb ramps are typically constructed 6' long when they are located at a 6" high curb and gutter - in assumption this would comply (based on my recent math calculation). - Unfortunately, this is a common assumption and is not accurate when we have additional "hidden" slopes.

Let's take a retail center for example.  It has a walkway along the front of the building roughly at 2% or 1/4" per foot from the face of the building to the back of curb. Here's the problem: When a 6' curb ramp is installed, it will end up with an additional 1-1/2" increase in height due to the sloping walkway and a running slope of 10.5%.  

Indicating 1:12 max on construction documents may be technically correct (although it still is not the least possible slope), but may also require additional direction for the actual construction of curb ramps. 
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